The present application relates generally to the manufacture of microelectronic components, and more specifically to no clean flux compositions and methods for soldering, such as in the assembly of integrated circuit modules and integrated circuit boards.
During the manufacture of microelectronic components, electrical connections are made, for example, between a single or multiple chips and a substrate. In an example manufacturing process, a chip is soldered directly to a substrate such as a laminate. In such manufacturing processes, a soldering flux is typically used to help fuse the elements being electrically connected. The soldering flux reacts with and eliminates surface oxides or impurities and protects the surfaces being soldered against further oxidation during soldering. The soldering flux may also improve wettability of the solder.
In a soldering process, solder bumps or metal pads on respective components to be joined are aligned and temporarily held in place with a tacky soldering flux. During the subsequent reflow process, the assembly is heated to melt the solder and form metallurgical bonds and electrical connections. To improve reliability, an underfill material can be used to fill the gap between the soldered components. The underfill material decreases the impact of thermal stresses that may otherwise compromise the solder joint and/or fragile materials that are present within one of the components, such as low-k dielectric materials that are used within a chip.
Fluxes in use by the microelectronics industry for automated soldering of printed circuit assemblies typically contain corrosive organic acids or components that, upon heating and dissipation of the flux, leave a decomposition residue that if un-cleaned will adversely impact adhesion of the underfill material to one or both of the components being joined and may also negatively impact the electrical contact resistance across the solder joint. Effective removal of such residue can be challenging in view of the narrow gap dimensions between the soldered components. Moreover, a step of residue removal adds time and expense to the soldering process.
In view of the foregoing, it would be advantageous to provide a no clean flux composition that does not require a cleaning process to remove flux residue from the device after reflow.